Polishing machine or similar abrading apparatus

ABSTRACT

A POLISHING MACHINE OR SIMILAR ABRADING APPARATUS HAVING A HORIZONTAL PLATEN ROTATABLE ABOUT A VERTICAL AXIS WITH WORKPIECES HELD AGAINST THE PLATEN BY AT LEAST ONE VERTICALLY MOVEABLE SUPPORT HEAD. COOLING MEANS ARE PROVIDED TO MAINTAIN THE OPERATING TEMPERATURE OF THE WORKPIECES AT DESIRED LEVELS BY CIRCULATING COOLANT THROUGH THE PLATEN AND THE SUPPORT HEAD.

Oct. 12, 1971 J. L. WEBER ETAL 3,611,654

POLISHING MACHINE OR SIMILAR ABRADING APPARATUS 5 Sheets-Sheet 1 Filed Sept. 30, 1969 m m Om JNVENTURS JOHN L. WEBER CARL J VELLA d. 12, 1971 J WEBER E.TAL 3,611,654

POLISHING MACHINE OR SIMILAR ABRADING APPARATUS Filed Sept. 30, 1969 5 Sheets-Sheet 2 XNVENTURS JOHN L. WEBER CARL. J- VELLA POLISHING MACHINE OR SIMILAR ABRADING APPARATUS Filed Sept. 30, 1969 Oct. 12, 1971 J. 1.. WEBER ETAL 3 SheetsSheet 5 INVENTORS JOHN L. WEBER CARL J VELLA Unit 3611,654 PLISHIN G MACHINE R SIMIILAR AIBRADHNG APPARATUS John L. Weber, Spencerport, and Carl .l. Vella, Rochester,

N.Y., assignors to Alliance Tool & Die Corp., ]Rochester, N.Y.

Filed Sept. 30, 1969, 561. Nu. 862,219 lint. Cl. 132411 55/02 U.S. Cl. 51-266 15 Claims ABSTRACT OF THE DISCLOSURE A polishing machine or similar abrading apparatus having a horizontal platen rotatable about a vertical axis with workpieces held against the platen by at least one vertically moveable support head. Cooling means are provided to maintain the operating temperature of the workpieces at desired levels by circulating coolant through the platen and the support head.

Crossreference is made to copending application Ser. No. 862,423, entitled Polishing Machine or the Lke With a Removable Platen, filed on even date herewith in the names of John L. Weber and George C. Klimas.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to abrading apparatus such as polishing or lapping machines, and in particular to cooling means in the machines to maintain desired Workpiece temperatures during operation.

Description of the prior art When polishing workpieces such as silicon or germanium semiconductor waters, it is important to maintain a pre selected temperature range to prevent damage to the sub surfaces of the wafers. Higher temperatures also reduce the uniformity of applied polishing material and can constitute a hazard to operation. Heretofore, certain kinds of lapping machines designed for other purposes have been modfied to perform such polishing operations, but operation has been at slow speeds in such equipment to prevent high operating temperatures that can cause damage to the workpieces or create undesired hazards. These machines also need to be shut down for long periods for cooling parts between operations. U.S. Pat. No. 2869,294 describes one cooling system developed for such lapping machines, but no known machine has overall uniform cooling for eflcient operation of machines of this kind.

SUMMARY OF THE INVENTION According to the present invention, a coolant, preferably water, is circulated through the platen in a controlled path and through the support heads, the coolant either being recirculated through a refrigerating system or dischar=ged. The platen assembly and supporting heads are specifically designed to maintain a -full head of water in each part with uniform levels to transfer heat from the work area 'with minimum temperature gradient changes.

Patentedl clt. 12, 1971 BRIEF DESCRIPTION OF THE DRAWING The invention as well as objects and advantages thereof will become more apparent from the course of the following description of a preferred embodiment, the accompanying drawing forming a part thereof and wherein:

FIG. 1 is a partial perspective view of a polishing machine embodying the present invention;

FIG. 2A is a partial elevational. view showing a workpiece head according to the invention in cross section;

FIG. 2B is a detail showing the support head lifting mechanism;

FIG. 3 is a detailed cross sectional view of the platen to show the cooling path;

FIG. 4 is a partial top view showing an end idler and its support head water discharge duct; and

FIG. 5 is a schematic view of the machine showing the fluid paths.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a polishing machine incorporating the present invention suitably includes a support frame 10 on top of which is mountecl a work table 11 about waisthigh to an operator. The work table 11 defines a central circular opening 12 within which is located a horizontally disposed circular platen assembly 13 rotatable about a central vertical axis. Work pieces are positioned on the top surface of the platen assembly 13, or a polishing pad covering the platen, and are held aganst the platen by a plurality (3) of work supporting heads 14 which are vertically moveable by a pneumatic system located in a control head unit 15 supported by a hollow column 16 forming part of the frame 10. In the operating position as shown in FIG. l, a plurality of idlers 17 frictionally engage collars 20 on support heads 14 to transmit uniform werking rotational moton to all of the workpieces.

The control unit contains suitable control device means to operate the polishing machine, such as a pneumatc control knob 22 for each support head 14 to raise and lower the head, water valves 23 to control the flow of water through the support heads, a slurry feed button 24 which provides a polishing compound in the form of a slurry to be pumped from a reservoir and metered onto the work surface of the platen, machine start and stop buttons 25, 26, a timer 27 and timer reset button 28 and an emergency stop 29. The side of the control head not shown includes two pneumatic control knobs 22, a water valve 23 and an emergency stop 29. Additional control buttons may include a refrigerating unit start button 31 and a circulating water pump or aspirator control button 32.

According to the present invention, each support head 14 is designed to provide cool water circulating through it to remove heat generated during a polishing operation. As shown in FIG. 2A, the head 14 comprises a main body portion 35 having a central bore within which is located a hollow tube 36. The tube 36 extends above body portion 35 to define a reference post for attaching a plurality of semicylindrical weights 37, which are added or removed to adjust the level of working pressure desired. A cylindrical cap 38 overlies the weights 37 to keep them on portion 35 while the head rotates. The cap is lifted to add or remove the weights as desired.

The lower end of tube 36 defines a flange.40 which is fixed by 1bolts or the like to a collar portion 41. Fixed to the center of collar 41 is an aligning stud 42, around which are located a plurality of ports 43 which provide fluid communication to the lower surface 44. The lower surface 44 is recessed as shown, and at the periphery of the recess are a plurality of fluid ports 45 to direct fluid from the lower surface to an annular space 46 defined by body portion 35 and the outer wall 47 of collar 41.

Within tube 36 is a hollow lifting tube 49 connected at its upper end to a hollow pneumatic piston 50 by joint coupling 51. The lower end of tube 49 defines a flange 52 which enga-ges flange 40 on tube 36 to raise the head 14 when tube 49 is lifted. In the down position as shown, flange 52 is spaced from flange 40 and body portion 35 such that the pneumatic system does not afi'ect the head pressure determined by weights 37.

As shown in FIG. 2B, the pneumatic system includes a cylinder 54 and suitable air pressure lines 55, 56 connected to a known air pressure source (not shown) by a valve controlled by knob 22 to selectively raise or lower the piston 50. A flexible Water line 58 connects the top portion of piston 50 to supply coolant water to the head.

T operate the machine, workpieces 60 (i.e. silicon wafers) are attached to the lower surface of a disc shaped mountng block 61 by a known adhesive such as wax. The block 61 is then placed on platen assembly 13 below a head 14 with the workpieces 60 against the platen surface. The upper surface of block 61 defines a centering hole 62 which is engaged by stud 42 when the head 14 is lowered to align the block 61 with the head 14. An

O-ring in a groove on the lower surface 44 of collar 41 provides a water seal in the operation position.

Coolant water enters each head through piston 50 and tube 49 and passes through center ports 43 to the space between the recessed portion of surface 44 and block 61 where it removes heat from the workpieces and block. The water then flows through peripheral ports 45 to the annular space 46 and removed from the space by a suction nozzle 63 connected to an aspirator pump actuated by button 32. The nozzle 63 is shaped to remain in position during rotation of collar 41.

Referring to FIG. 3, the lower platen assembly 13 supported by a hollow rotating spindle 65 passing through a support plate 66 in the frame 10. A gear box 67 transmits rotary motion to spindle 65 from a rnain drive motor 68 by suitable bevel gears 69, 70.

The platen assembly.l3 comprises a platen disc 72 which is detachably connected by set screws in lugs 74 to a platen support member 75. The platen support member 75 is fixed to a flange 76 which in turn is welded to the central spindle 65.

The platen disc 72 and platen support member 75 define an internal chamber 77 with a central water path deflecting plate 78 located in the middle of the chamber 77 and supported by a spacing block 79 fixed to the support member 75. The lower surface of the platen disc 72 is recessed at 80, whereas the spacing block 79 extends upwardly from the platen support member 75 to define a continuation of spindle 45 with its upper surface located above the lower surface of platen disc 72 as shown.

Spindle 65 is hollow and within the spindle are located an inlet water line 81 and an outlet water line 82 through a water-tight divider 83 within the spindle 65 as shown. The water inlet line 81 is directed to supply the upper region of spindle 65 with coolant water which passes through the plurality of spaced ports 84 around the periphery of spindle 65. Water from the ports 84 then flushes radially outward along the lower portion of chamber 77 around the plate 78 and along the portion of the chamber above plate 78 to the center recessed portion 80 of platen disc 72 where it is discharged through the outlet line 82. As can be seen, the recessed portion 80 and the extension of spacing block 79 constrain the flow of water to maintain a full level within the platen cooling chamber 77 to assure that all portions of the platen disc 72 are cooled continuously. Coolant water is supplied to the inlet line 81 under pressure from a main water line or from the refrigeration unit by inlet 84. The water is removed by flowing from the outlet line 81 along the spindle through a discharge duet 85 to a waste line or to be recirculated through the refrigerating unit.

A hollow statonary shaft extension 87 fixed to gear box 67 and a stationary inlet water line portion 88, both with suitable fluid sealing means to permit relative rotation of the spindle 65 and line 81, are provided to complete the coolant paths between the platen assembly 13 and the inlet line 84 and outlet duct 85.

Support of spindle 65 is provided by a support collar 89 mounted on plate 66. Collar 89 retains a taper roller hearing 90 of the type that provides hearing support for spindle 65 while allowing thrust produced by the weight of platen assembly 13 through flange 76. Suitable fluid seals 91 with an excess fluid discharge line 92 are included.

Also known in FIG. 3 is an annular drain pan 94 surrounding the platen assembly 13 to collect slurry and other waste materials developed during machine operation, as well as the standing water in each support head after operation when the mountng block 61 and attached workpieces are removed. The lower end of pan 94 is inclined toward a drain line 95.

To complete the coolant water discharge system in relation to the upper support heads 14, each nozzle 63 is connected to an outlet line 96 by a hollow portion of an idler support column 97 fixed to support plate 66. Nozzle 63 is slideably supported in column 97. Referring also to FIGS. 2A and 4, each idler 17 is rotatably supported by a block 98 pivotally supported about a pin 99. A liftable locating pin 100 in its seated position retains block 98 in its operating position as shown in solid lines in FIG. 4 but when raising of the support head 14 is desired, nozzle 63 is lfted to clear wall 47 and locating pin 100 also lifted to pivot the idler assembly to the dotted line position of FIG. 4.

As is described in copending application S.N. 862,423 entitled, Polishing Machine or the Like With a Remov able Platen, filed on even date herewith, the platen disc 72 may be removed by a suitable hoist mechanism located in machine head 15 with a hook end to engage pins on a center idler post assembly 106 that is fixed to platen disc 72 (see'FIG. 2A). The center idler assembly as shown rotatably supports an idler wheel 107 that engages each of the three collars 41 to maintain uniform rotary moton for the three support heads.

FIG. 5 shows a side view of the polishing machine in phantom with the coolant and slurry feed systems according to the invention. Slurry feed is provided by a sup ply tank 110 on a support platform 111 at the rear of the machine. Any known abrasive or polishing compound in slurry form (e.g. 50% compound, 50% water) and used for this purpose is fed through a supply line 112 by an electrical feed pump 113 controlled by button 24 to a plurality (three) of flexible feed tubes 114 positioned to meter the polishing compound at a desired metered rate to each head, say 100-300 drops per minute per tube. Alternatively, it may also be possible to direct polishing slurry to the work area by placing the end of a tube 114 in the central blind opening 115 of center idler post assembly 106, such that slurry is fed to platen disc 72 by feed ports 115 at the bottom of opening 115.

Coolant water is supplied from an outside water tap line 116 with a suitable master control valve to a T- connection 117 where water is dstributed by a line 118 to the support heads, a line 119 to the platen assembly and a flexible line 120 to a portable hand nozzle 121 10- cated on the work table 11 to provide manna] cleaning or flushing of the machine working surfaces. Line 118 feeds water to a junction box 122 where three lines 123 separately feed water to each of the support heads through a respective control valve 23 and flexible line 58. Line 119 in turn feeds water to the inlet port 84 of the lower shaft portion 87.

Discharge of water in turn is accomplished by the three support head outlet lines 96 drawing a suction developed by an electrical aspirator pump 125, which is electrically controlled by button 32 as described to dscharge water through duet 126 to the drain line 95 which also drains pan 94l. Drain line 95 and platen outlet duet 85 in turn join to a common outside water discharge line at 127.

In a further form of the invention, the cooling system may be provided with a recirculating refrigerating system to receive water from the discharge lines and after cooling to a desired temperature recirculates the water through the machine. The refrigerating system as shown in dotted lines in FIG. comprises a Water reservoir tank 130 to receive discharge Water by lines 126 and 85' from the support heads and platen, respectively. Water from the reservoir tank 130 in turn is fed by a line 131 to a r frigerating unit 132 where it is cooled to the desired temperature as determined by a temperature control thermostat 133 located on the support column 16 as shown. A circulating pump 134 then directs water through lines 118 and 119 to the support heads and platen respectively. Thus, in lieu of the direct lnes 118 and 119, water is supplied from outside at T-connection 117 to the reservoir 130 by a line 135, and an overflow line 136 to drain 127 is included in lieu of ducts 126 and 85. Any suitably known water level control to maintain the desired water level in tank 130 by controlling the master valve to intermittently supply water as required from tap line 116 can be used.

Depending upon the workpieces to be polished, water temperature can be controlled at any desired level of between, say 44 to 120 F., and with about a 16 range at the desired setting. A refrgerating unit with about 13,000 B.t.u. capacity easily supples this need.

Thus, it can be seen that a uniform and eflicient cooling system has been provded to polishng machines or similar abrading apparatus of the class describecl.

While the invention has been descrbed by reference to a preferred embodiment, it is evident that changes or modifications, for example with respect to size, shape or arrangement of parts, may be resorted to without departing from the spirit of the invention.

We claim:

1. Abrading apparatus comprising: a rotatable platen assembly supporting workpieces to be abraded, the platen assembly having means including a workpiece supporting platen portion and a support portion defining therebetween a flud chamber, means for dividing the chamber into two distnct flud chamber portions with one chamber portion contiguous with the platen portion and the other chamber portion spaced from the platen portion, the dividing means including edge means for providing flud communication between the chamber portions at peripheral areas of the platen assembly, and flud feed means for feeding a temperature controllng flud into one of the two chamber portons around the edge means to the other of the two chamber portions and then discharging said flud from the chamber.

2. Abrading apparatus according to claim 1 wherein the platen assembly defines a generally cylindrical shape with the platen portion comprising an upper end wall and the support portion comprising a lower end wall, and the dividing means comprises a solid disc located between the end walls and spaced from the cylindrical side wall.

3. Abrading apparatus according to claim 2 wherein the dividing means further comprises a spacer block be tween the disc and support portion, the spacer block defining at least one flud port to direct flud from the feed means only into the chamber portion spaced from the platen portion and at least one port to discharge flud only from the chamber portion contiguous with the platen portion.

4. Abrading apparatus according to claim 3 wherein the flud is a liquid and the platen assembly is disposed horzontally for rotation about a vertical axis with the platen portion located above the support portion, the inner side of platen portion end wall defining a generally flat wall and a central recessed area, the upper end f the spacer block being located at a level higher than the flat wall area with the discharge port opening to the contguous chamber above the flat wall to maintain liquid at a level engaging at least the e=ntire fiat wall area of the platen portion.

5. Abrading apparatus according to claim 4 and further comprising a hollow spindle connected to the upport portion and drive means to rotate the platen assembly by the hollow spindle, the flud feed means including inlet and outlet lines located within the hollow spindle and communicating respectively with the flud directing port and the flud discharge port.

6. Abrading apparatus comprising a horizontal platen assembly for supporting workpieces to be abraded and rotatable about a vertical axis, and at least one workpiece retaining support head for constraining movement of the workpieces relative to the platen assembly, the support head comprising: a collar portion, a detachable work retaining block portion, the block portion and collar portion comprising means for algning the block portion on attachment, means including the collar portion and block portion to define a flud space with inlet and outlet ports, and means for feeding a temperature controlling flud into the space through the inlet port and discharging the flud from the space by the outlet port.

7. Abrading apparatus according to claim 6 comprising a body portion defining a central bore communicating with the inlet port and the collar portion includes an annular wall to define an annular space between the body portion and collar portion, the collar portion defining the outlet port to provide flud communication between the flud space and the annular space.

8. Abrading apparatus according to claim 7 wherein the flud feeding means includes a flud discharging nozzle located in the annular space to withdraw flud from the annular space.

9. Abrading apparatus according to claim 6 wherein the support head is movable and further comprising oper able movng means for selectively rasing and lowering the head, a body portion defining a central bore and the movng means comprising a hollow flud transmitting tube extendng in the bore and including flange means cooperatively engaging the body portion to raise the support head when operating the movng means.

10. Abrading apparatus comprising: a movable platen assembly including a support portion and a platen portion having a working surface to receive workpieces to be abraded, the platen portion and support portion defining a chamber therebetween; a workpiece support head movable relative to the platen assembly, the support head including a removable collar portion and a workpiece block portion holding workpieces to constrain movement of the workpieces, the collar portion and block portion defining a space therebetween; and means for feeding a cooling flud through the chamber and through the space to withdraw heat generated by abrading.

11. Abrading apparatus according to claim 10 wherein the platen assembly further includes a plate within the chamber t0 divide the chamber into a first chamber portion adjacent the platen portion and a second chamber portion spaced from the platen portion, the cooling flud being fed to the first platen portion from the second platen portion by passing around the plate.

12. Abrading apparatus according to claim 11 wherein the platen portion and the plate are crcular and rotate about a vertical axis, the coolng flud being a liquid and the platen assembly further defining a spacer block having a flud outlet port to discharge flud from the first chamber porton and located to mantan a level of water engaging the platen portion at least along the entire orkng surface of the platen porton.

13. Abrading apparatus accordng to claim 10 wherein the collar p0rton defines at least one flud inlet port and at least one flud outlet port.

14. Abrading apparatus accordng to claim 13 wherein the cooling flud is a liquid, and the collar portion further comprises an annular wall to form a reservoir to receive liqud from the outlet port, and nozzle means for discharging liquid from the reservoir.

15. Abrading apparatus according to claim 14 wheren the support head defines a central bore communicatng with the inlet port and comprising a pluralty of outlet ports connecting the space to the reservoir.

Referehces Cited UNITED STATES PATENTS 2,869,294 1/1959 Boettcher et al 51266 2,532,581 12/1950 Triggs 51266 3093937 6/1963 Balamuth et al 51-131 10 WILLIAM R. ARMSTRONG, Prmary Examiner U.S. C1. X.R. 51-131 

